Implement input type configs (#3784)

Add support for configurations that apply to a type of inputs
(i.e. natural scrolling on all touchpads). A type config is
differentiated by a `type:` prefix followed by the type it
corresponds to.

When new devices appear, the device config is merged on top of its
type config (if it exists). New type configs are applied on top of
existing configs.

sway/sway-input.5.scd

@@ -9,13 +9,28 @@ sway-input - input configuration file and commands
 Sway allows for configuration of devices within the sway configuration file.
 To obtain a list of available device identifiers, run *swaymsg -t get_inputs*.
 Settings can also be applied to all input devices by using the wildcard, _\*_,
-in place of _\<identifier\>_ in the commands below.
+in place of _\<identifier\>_ in the commands below. In addition, the settings
+can be applied to a type of device, by using _type:\<input_type\>_ in place
+of _\<identifier\>_.
 
 Tip: If the configuration settings do not appear to be taking effect, you could
 try using _\*_ instead of _\<identifier\>_. If it works with the wildcard, try
 using a different identifier from *swaymsg -t get_inputs* until you find the
 correct input device.
 
+Current available input types are:
+
+- touchpad
+- pointer
+- keyboard
+- touch
+- tablet_tool
+- tablet_pad
+- switch
+
+Note: The type configurations are applied as the devices appear and get applied
+on top of the existing device configurations.
+
 # INPUT COMMANDS
 
 ## KEYBOARD CONFIGURATION